Democratic leaders in the Senate and House have concluded that a government-run insurance plan is the cheapest way to expand health coverage, and they sought Friday to rally support for the idea, prospects for which have gone in a few short weeks from bleak to bright.

The shift in momentum is so dramatic that many lawmakers now predict that President Obama will sign a final bill that includes some form of government-sponsored insurance for people who do not receive coverage through the workplace. Even Democrats with strong reservations about expanding government's role in the health-care system say they are reconsidering the approach in hopes of making low-cost plans broadly available.

Senate Majority Leader Harry M. Reid (Nev.) and House Speaker Nancy Pelosi (Calif.) sought support Friday for expansive versions of the public option as they prepared to send reform legislation to the Senate and House floors. Their goal is to pass bills with similar versions of the public insurance option so that final talks between the two chambers can focus on other issues that could prove more difficult to resolve.

The public-option debate is frustrating some Democrats, who have come to believe that a government-run plan is neither as radical as its conservative critics have portrayed, nor as important as its liberal supporters contend. Any public plan is likely to have a relatively narrow scope, as it would be offered only to people who don't have access to coverage through an employer.

The public option would effectively be just another insurance plan offered on the open market. It would likely be administered by a private insurance provider, charging premiums and copayments like any other policy. In an early estimate of the House bill, the Congressional Budget Office forecast that fewer than 12 million people would buy insurance through the government plan.

Reid's original inclination was to leave the public option out of a final bill he is writing from measures passed by the finance and health committees. But his liberal colleagues began urging him two weeks ago to reconsider, after insurance industry forecasts that premiums would rise sharply under the Finance Committee bill, which lacked a public option. The report had the effect of prodding Democrats to look for better ways to control costs, and the public option -- strongly opposed by the insurance industry -- reemerged as a possible solution.

Because a government-run plan would be dedicated to holding down costs and would lack a profit motive, congressional budget analysts predict that it could reduce the cost of expanding coverage to people who don't have it by as much as $100 billion over the next decade.

In the House, Pelosi was still trying to line up votes for the most cost-effective version of the public plan, one that would pay providers based on Medicare rates. Rank-and-file House Democrats summoned Friday to an early-morning caucus were asked to say publicly whether they would vote for a bill that included such a provision.

The House of Representatives is about to bring its final healthcare reform bill to the floor. The vast majority of the Democratic Caucus supports the inclusion of a "robust" public option that would pay providers Medicare rates plus 5 percent, but resistance from a small portion of the caucus is threatening to derail the effort. These members want a bill with either no public option or a diluted public option based on expensive negotiated rates and phony triggers. It is crucial that a robust public option is included in the bill, and that no triggers are involved.

I, and more than 200 other House Democrats, believe that a public option should start out by paying Medicare rates plus 5 percent for the first three years because the Medicare formula is already public and well understood, and this will maintain transparency. After that, the legislation currently being considered in the House would allow the government to begin negotiating rates with providers in a manner consistent with the initial rate.

Some members prefer that a public option plan start out by negotiating payment rates with providers right away. However, Congressional Budget Office estimates show that a public option that negotiates rates with providers would only save the government an estimated $25 billion over the next ten years, versus $110 billion with Medicare-plus-five. Negotiating rates immediately would drive the public plan down a dangerous path by linking it to skyrocketing medical inflation, and would not foster the competition necessary for real cost reductions to consumers and up-front savings for the government. Just as importantly, under the negotiated rate plan, the government will have to make up any loss of coverage by putting more people into Medicaid. This will further burden states as well as greatly limit individuals' access to providers....

Any public option structured around a trigger would not create such competition, and would be problematic for several reasons. Passing a bill that forces Americans to buy insurance they may or may not be able to afford is not only terribly unfair as policy, it would provoke a huge political backlash and threaten any future efforts to improve the system further. At the same time, nothing would to stop Congress from continuously pushing back the trigger deadlines, just as we do now with Medicare Part D. A law that puts additional burdens on consumers while doing nothing to change the landscape of the insurance market is doomed to fail.